This invention relates to a dispersion of a dye in a solvent wherein the dye forms a lyotropic liquid crystalline phase, a method for preparing said dispersions, an imaging element containing said dispersion and a photographic element containing said dispersion.
Radiation-sensitive materials, including light-sensitive materials, such as photographic materials, may utilize filter dyes for a variety of purposes. Filter dyes may be used to adjust the speed of a radiation-sensitive layer; they may be used as absorber dyes to increase image sharpness of a radiation-sensitive layer; they may be used as antihalation dyes to reduce halation; they may be used to reduce the amount or intensity of radiation from reaching one or more radiation-sensitive layers, and they may also be used to prevent radiation of a specific wavelength or range of wavelengths from reaching one or more of the radiation-sensitive layers in a radiation-sensitive element. For each of these uses, the filter dye(s) may be located in any number of layers of a radiation-sensitive element, depending on the specific requirements of the element and the dye, and on the manner in which the element is to be exposed. The amount of filter dyes used varies widely, but they are preferably present in amounts sufficient to alter in some way the response of the element to radiation. Filter dyes may be located in a layer above a radiation-sensitive layer, in a radiation-sensitive layer, in a layer below a radiation-sensitive layer, or in a layer on the opposite side of the support from a radiation-sensitive layer.
Photographic materials often contain layers sensitized to different regions of the spectrum, such as red, blue, green, ultraviolet, infrared, X-ray, to name a few. A typical color photographic element contains a layer sensitized to each of the three primary regions of the visible spectrum, i.e., blue, green, and red. Silver halide used in these materials has an intrinsic sensitivity to blue light. Increased sensitivity to blue light, along with sensitivity to green light or red light, is imparted through the use of various sensitizing dyes adsorbed to the silver halide grains. Sensitized silver halide retains its intrinsic sensitivity to blue light.
There are numerous applications for which filtration or absorbance of very specific regions of light are highly desirable. Some of these applications, such as yellow filter dyes and magenta trimmer dyes, require non-diffusing dyes which may be coated in a layer-specific manner to prevent specific wavelengths of light from reaching specific layers of the film during exposure. These dyes must have sharp-cutting edges on the bathochromic (long-wavelength) side of the absorbance envelope to prevent light punch through without adversely affecting the speed of the underlying emulsions. In other applications, it is desirable to allow passage of light below a certain wavelength. In these cases it is desirable to have a dye which is very sharp-cutting on the hypsochromic (short-wavelength) edge of the absorbance envelope. Depending on the location of these filter layers relative to the sensitized silver halide emulsion layers, it would also be desirable to have non-diffusing, layer-specific filter dyes with absorption spectra which are sharp-cutting on the hypsochromnic edge as well as the bathochromic edge. Such dyes are sometimes known as xe2x80x9cfinger filtersxe2x80x9d. Preferably these dyes should exhibit high extinction coefficients, narrow halfbandwidths and sharp cutting hypsochromic and bathochromic absorption envelopes when incorporated into imaging elements including photographic elements. Typically, to achieve these properties, isotropic solutions of dyes have been incorporated. Dyes introduced by this method, however, often wander into adjacent layers causing problems such as speed loss or stain, and cannot be coated in a layer-specific manner without the use of mordants. Solubilized dyes may be mordanted to prevent wandering through adjacent layers. While the use of polymeric mordants can prevent dye wandering, such mordants aggravate the stain problem encountered when the dye remains in the element through processing.
Dyes with a high extinction coefficient allow maximum light absorption using a minimum amount of dye. Lower requisite dye laydown reduces the cost of light filtration and produces fewer processing by-products. Lower dye laydowns may also result in reduced dye stain in short duration processes.
Finger filters such as described above are highly desirable for other uses such as protecting silver halide sensitized emulsions from exposure by safelights. Such dyes must have absorbance spectra with high extinction coefficients and narrow halfbandwidths, and sharp cutting absorbance envelopes to efficiently absorb light in the narrow safelight-emitting region without adversely affecting the speed of the sensitized silver halide emulsions. This affords protection for the sensitized emulsion from exposure by light in the safelight""s spectral region. Useful absorbance maxima for safelight dyes include, but are not restricted to 490-510 nm and 590-610 nm.
Similar properties are required for infrared absorbing filter dyes. Laser-exposed radiation-sensitive elements require high efficiency light absorbance at the wavelength of laser emission. Unwanted absorbance from broadly absorbing dyes reduces the efficiency of light capture at the laser emission wavelength, and requires the use of larger amounts of dye to adequately cover the desired spectral region. In photographic elements, unwanted absorbance may also cause speed losses in adjacent silver halide sensitized layers if the photographic element has multiple sensitized layers present. Useful finger filter absorbance maxima for absorbing laser and phosphor emissions include but are not restricted to 950 nm, 880 nm, 830 nm, 790 nm, 633 nm, 670 nm, 545 nm and 488 nm.
In some radiation sensitive elements, including dry process imaging films, it is necessary to provide light filtration or antihalation at deep cyan and infrared wavelengths. Typically such protection has been achieved using water or solvent soluble dyes or milled solid particle dyes. Typically, water-soluble dyes forming isotropic solutions can provide relatively sharp, high extinction absorbance, but are prone to interlayer wandering.
One common use for filter dyes is in silver halide light sensitive photographic elements. If, prior to processing, blue light reaches a layer containing silver halide which has been sensitized to a region of the spectrum other than blue, the silver halide grains exposed to the blue light, by virtue of their intrinsic sensitivity to blue light, would be rendered developable. This would result in a false rendition of the image information being recorded in the photographic element. It is therefore a common practice to include in the photographic element a material that filters blue light. This blue-absorbing material can be located anywhere in the element where it is desirable to filter blue light. In a color photographic element that has layers sensitized to each of the primary colors, it is common to have the blue-sensitized layer closest to the exposure source and to interpose a blue-absorbing, or yellow filter layer between the blue-sensitized layer and the green- and red-sensitized layers.
Another common use for filter dyes is to filter or trim portions of the UV, visible or infrared spectral regions to prevent unwanted wavelengths of light from reaching sensitized emulsions. Just as yellow filter dyes prevent false color rendition from the exposure of emulsions sensitized to a region of the spectrum other than blue, filter dyes absorbing in the UV, magenta, cyan and infrared spectral regions can prevent false color rendition by shielding sensitized emulsion layers from exposure to specific wavelength regions. One application of this strategy is the use of green-absorbing magenta trimmer dyes. In one type of typical color photographic element containing a layer sensitized to each of the three primary regions of the visible spectrum, i.e., blue, green, and red, the green-sensitized layer is coated above the red-sensitized layer and below the blue-sensitized layer. Depending on the chosen spectral sensitivity maxima for the sensitized silver halide layers, there may be a region of overlap between the spectral sensitivities of the green and red emulsions. Under such circumstances, green light which is not absorbed by the green-sensitive emulsion can punch through to the red sensitive emulsion and be absorbed by the leading edge of the red spectral sensitizing dye. This crosstalk between the green and red emulsions results in false color rendition. It would, therefore, be highly desirable to find a green-absorbing filter dye which upon incorporation into a photographic element would absorb strongly around the spectral maximum of the green-sensitized emulsion, and possess a sharp cutting bathochromic absorbance such that there is no appreciable absorbance just bathochromic to its absorbance maximum. A sharp-cutting bathochromic edge on a filter or trimmer dye enables excellent color reproduction with minimum speed loss by absorbing light efficiently up to its absorbance maximum, but very little if any just past its absorbance maximum. For example, a magenta trimmer dye (green absorber) which is only moderately sharp-cutting on the bathochromic edge may function adequately as a filter dye, but its unwanted absorbance in the red region past its xe2x96xa1max will rob the red-sensitive emulsion coated below it of red light and hence speed. Though the position of optimal absorption maximum for a magenta trimmer dye will vary depending on the photographic element being constructed, it is particularly desirable in one type of typical color photographic element containing a layer sensitized to each of the three primary regions of the visible spectrum, i.e., blue, green, and red, that a magenta trimmer dye absorb strongly at about 550 nm, and possess a sharp cutting bathochromic absorbance such that there is no appreciable absorbance above about 550 nm. Therefore it would be desirable to provide a filter dye for use in photographic elements that possesses high requisite absorbance in the green region of the spectrum below about 550 nm, but little or no absorbance above about 550 nm, and furthermore does not suffer from incubative or post process stain problems, and furthermore is not prone to migration in the coated film, but is fully removed upon processing.
One method used to incorporate solvent or water-soluble filter dyes into photographic film element layers is to add them as aqueous or alcoholic isotropic solutions. Dyes introduced by this method are generally highly mobile and rapidly diffusing and often wander into other layers of the element, usually with deleterious results. While the use of polymeric mordants can prevent dye wandering, such mordants aggravate the stain problem encountered when the dye remains in the element through processing.
Filter dyes have also been prepared as conventional dispersions in aqueous gelatin using standard colloid milling or homogenization methods or as loaded latices. More recently, ball-milling, sand-milling, media-milling and related methods of producing fine-particle-size slurries and suspensions of solid filter dyes have become standard tools for producing slurries and dispersions that can readily be used in photographic melt formulations. Solid particle filter dyes introduced as dispersions, when coated at sufficiently low pH, can eliminate problems associated with dye wandering. However, solvent- insoluble solid particle filter dyes (pigments) provide relatively low absorption coefficients, requiring that an excessive amount of dye be coated. In addition, it is very difficult to find classes of solid particle dispersion dyes which consistently yield useful, sharp-cutting bathochromic or hysochromic spectral features due to their microcrystalline nature. In fact the hue of a microcrystalline dye is highly unpredictable and often varies tremendously between similar analogs. In addition many solid particle dyes are not robust under keeping conditions of high heat and humidity experienced in melting and coating operations. Under such conditions, microcrystals of dye can undergo ripening, resulting in a lower optical density post incubation. In addition, the time and expense involved in preparing serviceable solid particle filter dye dispersions by milling techniques are a deterrent to their use, especially in large volume applications. It is therefore desirable to provide dye dispersions that do not necessarily require mechanical milling before use and that do not wander but that wash out easily during processing leaving little or no residual stain. It is also desirable that such filter dye dispersions provide high light absorption efficiencies with sharp-cutting absorbance peaks. One method of obtaining these desirable dye features in solid particle dispersions of oxonol filter dyes was described by Texter (U.S. Pat. Nos. 5,274,109, 5,326,687 and 5,624,467). Texter describes a process by which pyrazolone oxonol dyes are microprecipitated under strictly controlled pH conditions to produce absorbance spectra which are narrow, bathochromic and sharp cutting on the long wavelength side relative to their corresponding milled solid particle dispersions. This technique, however, is impractical for large volume applications.
A specific class of dyes, barbituric acid oxonol dyes, have been disclosed in commonly assigned copending U.S. application Ser. No. 08/565,480 filed Nov. 30, 1995, the entire disclosures of which are incorporated herein by reference, and U.S. Pat. No. 5,766,834 to possess sharp-cutting spectral properties when incorporated into gelatin coatings; however no reference is made to suggest that other filter dye classes might possess these useful spectral features. Further, the spectral features of these dyes are limited to a few specific wavelength ranges, and the hue of these sharp-cutting dyes are not tunable over a large useful range.
It would be very useful if dye materials were available that were non-wandering, like solid particle dispersions, but were additionally narrowly absorbing and sharp-cutting in spectral features, like fully solvent-soluble dyes, and were additionally available at a wide variety of absorbance maxima useful in imaging elements.
It is therefore desirable to have a dye, especially a filter dye, which has a high extinction coefficient, a narrow halfbandwidth, and is sharp cutting on the bathochromic and/or hypsochromic edge, and even more preferably on both the hypsochromic and bathochromic edges. For dyes used in photographic elements, it is additionally desirable that the dye is capable of being substantially completely removed or rendered colorless on process of an exposed radiation-sensitive element comprising said dye. It is also desirable that the coated dye be robust in its spectral and physical properties and not prone to migration within the imaging element. It is also desirable to have a method for preparing a dispersion of a filter dye that is suitable for high-volume manufacture.
It has now been discovered that merocyanine dyes derived from a broad range of activated methylene nuclei may be functionalized with certain substituents and solubilizing groups, and dispersed in hydrophilic colloids to form lyotropic (solvent-induced) liquid-crystalline dye phases (mesophases). These mesophase-forming dyes possess unique and useful properties superior to those of conventional water or solvent-soluble dyes or solvent-insoluble solid particle dyes with respect to hue, spectral shape, immobility, robustness and process removability. Additionally it has been discovered that for a given dye class, one skilled in the art can optimize dye analogs such that they possess an inherent propensity to form stable liquid-crystalline phases rather than microcrystalline (solid) or isotropic (e.g. solution) phases when dispersed in solvents, including hydrophilic colloids such as aqueous gelatin. Additionally it has been discovered that modifications in the properties of the hydrophilic colloid dye dispersion, such as ionic strength, temperature and pH can improve a given dye""s propensity to form a stable liquid-crystalline phase. Additionally it has been discovered that the advantageous spectral and physical properties of the dye liquid crystalline phases formed in the wet hydrophilic colloid (e.g. aqueous gelatin) are largely retained in the dried-down (evaporated) gelatin coatings of an imaging element.
This invention relates specifically to amphiphilic dyes, especially filter dyes in photographic elements which are capable of forming practically useful lyotropic liquid-crystalline phases, particularly dyes from the merocyanine classes. However, it is anticipated that liquid crystal formation is not necessarily restricted to these particular dye classes nor specific dye structures. This technology may also be applied to any novel merocyanine dye structure with potentially useful photographic filter properties. It is understood that the degree of amphophilicity to be imparted to a particular dye chromophore by the incorporation of said solubilizing groups will vary from chromophore to chromophore and from dye class to dye class.
Liquid-crystalline filter dyes afford a host of benefits over conventional state-of-the-art solid particle (microcrystalline)-incorporated dyes or water-soluble (isotropic solution) filter dyes, for photographic imaging applications. Moreover, they provide a combination of spectral and physical properties that is virtually unachievable using either water-soluble or solid particle dyes. The following beneficial spectral and physical properties are inherent to the liquid-crystalline form of the dye. For example, dyes dispersed in a lyotropic liquid-crystalline form exhibit slow collective molecular diffusion (orders of magnitude slower than dye isotropic solution species) affording good layer specificity and immobility, like (microcrystalline) solid particle dyes and unlike unmordanted isotropic solution dyes. Dyes dispersed in a lyotropic liquid-crystalline form exhibit significantly higher extinction coefficients than (microcrystalline) solid particle dyes dispersed at equivalent wet laydowns (concentrations). Dyes dispersed in a lyotropic liquid-crystalline form show processing washout and bleaching rates comparable to, but usually much better than, conventional (microcrystalline) solid particle dyes. Lyotropic liquid-crystalline dye phases are more easily, rapidly and reproducibly formulated than (microcrystalline) solid particle dye phases. Dyes dispersed in a lyotropic liquid-crystalline form, (especially the smectic mesophase form), often exhibit sharper-cutting, more intense spectral absorption features than their (microcrystalline) solid particle counterparts, making them particularly useful as photographic finger filters. Dyes dispersed in a lyotropic liquid-crystalline form often exhibit characteristic bathochromically-shifted excitonic absorption J-bands (sharp, narrow and intense), possessing (long-wavelength) sharp-cutting spectral features, making them particularly useful for many photographic finger-filter applications. So-called J-band (J-aggregate) spectra are not readily afforded by (microcrystalline) solid particle dyes. Dyes dispersed in a lyotropic liquid-crystalline form may also exhibit practically useful hypsochromically-shifted H-band absorption spectra, with (short-wavelength) sharp-cutting spectral features. Dyes dispersed in a lyotropic liquid-crystalline state may also exhibit little or no spectral shift compared with the dye""s isotropic solution absorbance state, yet still retain the characteristic immobility of the liquid crystalline phase. The essentially xe2x80x9cimmobilexe2x80x9d lyotropic liquid-crystalline form (phase) of the preferred amphiphilic filter dyes, exhibiting characteristic and practically useful J-band and H-band absorption spectra, are quite distinct, easily identifiable and readily distinguishable from non-liquid-crystalline (isotropic) rapidly-diffusing dye phases which occasionally exhibit similar absorption spectra. Dyes dispersed in a lyotropic liquid-crystalline state in aqueous, or those dyes passing through a transitory mesophase upon the drying of aqueous gelatin layers, usually retain the useful spectral and physical properties associated with the mesophase in the evaporated (dried-down)state. Dyes initially dispersed as a lyotropic liquid-crystalline form often exhibit good incubation stability in evaporated gelatin layers.
This invention comprises a collection of merocyanine dyes, derived from a wide variety of activated methylene nuclei, which can form lyotropic liquid crystals when selectively functionalized as described below. This disclosure further teaches one skilled in the art how to find liquid-crystalline members of a given dye class; it further includes test protocol for determining the presence of a dye mesophase (i.e. liquid crystal phase), and shows the superior features dye liquid crystals possess compared with solid particle dyes or solvent-soluble (solution) dyes. This invention further demonstrates the advantages of dye mesophase properties in imaging elements, especially photographic elements.
One aspect of this invention comprises a filter dye which when dispersed in a solvent, especially water or a hydrophilic colloid such as aqueous gelatin, forms a liquid-crystalline phase.
Another aspect of this invention comprises a filter dye which when dispersed in a solvent or a hydrophilic colloid such as aqueous gelatin, forms a smectic liquid-crystalline phase.
Another aspect of this invention comprises a filter dye which when dispersed in a solvent or a hydrophilic colloid such as aqueous gelatin, forms a nematic or hexagonal liquid-crystalline phase.
Another aspect of the invention comprises a dye lyotropic liquid-crystalline which exhibits a spectral absorbance maximum bathochromically or hypsochromically shifted, and exhibits an unusually high extinction coefficient and an exceptionally narrow halfbandwidth relative to its isotropic monomeric solution state.
Another aspect of the invention comprises a dye lyotropic liquid-crystalline phase which possesses a spectral absorbance envelope with an extinction coefficient and halfbandwidth similar to its isotropic monomeric solution state.
Another aspect of this invention comprises a filter dye which when dispersed in a hydrophilic colloid such as aqueous gelatin to form a liquid-crystalline phase, possesses a narrow spectral absorption band exhibiting an especially sharp-cutting short or long wavelength edge.
Another aspect of this invention comprises a filter dye which when dispersed in a hydrophilic colloid such as aqueous gelatin to form a liquid-crystalline phase, possesses a narrow spectral absorption band exhibiting especially sharp-cutting short and long wavelength edges.
Another aspect of this invention comprises a filter dye which when dispersed in a hydrophilic colloid such as aqueous gelatin to form a liquid-crystalline phase, exhibits low dye diffusibility and interlayer wandering.
Another aspect of this invention comprises a direct gelatin dispersion method allowing easy, inexpensive, rapid and reproducible incorporation of the inventive dyes in the liquid-crystalline state, with all desirable properties intact, into imaging elements, especially photographic elements without recourse to milling techniques.
Another aspect of this invention comprises a filter dye which when dispersed in a hydrophilic colloid such as aqueous gelatin to form a liquid-crystalline phase exhibits excellent stability at high temperature and humidity conditions.
Another aspect of this invention comprises a filter dye which when dispersed in a wet hydrophilic colloid such as aqueous gelatin to form a liquid crystalline phase retains all of the desirable physical and spectral properties once the coated imaging element is dried-down (evaporated).
Another aspect of the invention comprises a silver halide radiation-sensitive material containing at least one dye in the liquid-crystalline state, dispersed in a hydrophilic colloid layer, which is decolorized by photographic processing and which causes no deleterious effects on the silver halide photographic emulsions before or after processing.
A further aspect of the invention comprises a silver halide radiation-sensitive material in which a hydrophilic colloid layer is dyed and exhibits excellent decolorizing properties upon photographic processing.
Yet another aspect of the invention comprises a silver halide radiation-sensitive material in which a hydrophilic colloid layer is dyed and exhibits high absorbance in a portion of the spectral region at its absorbance maximum, but possesses comparatively little absorbance around 20 nm above its absorbance maximum.
Yet another aspect of the invention comprises a silver halide radiation-sensitive material in which a hydrophilic colloid layer is dyed and exhibits high absorbance in a portion of the spectral region at its absorbance maximum, but possesses comparatively little absorbance around 20 nm below its absorbance maximum.
We have now discovered that certain dyes set forth below form stable liquid-crystalline phases when dispersed in wet aqueous media (preferably containing a hydrophilic colloid such as gelatin) and provide the advantages set for in the above objects of the invention. The said liquid-crystalline dye dispersion can be formed by dispersing powdered dye or a milled dye slurry into an aqueous medium, preferably containing gelatin or other hydrophilic colloid, over a specified concentration and temperature range, using the methods set forth herein.
One aspect of this invention comprises a solvent, preferably an aqueous medium, having dispersed therein a liquid-crystal forming dye of structural Formula I:
[Dxe2x80x94(X)m]xe2x80x94(Y)n
wherein
D is a merocyanine dye.
Each Y contains an ionic or a nonionic solubilizing substituent or a group with a pKa value of less than 4 in water.
Each X is a nonionic substituent.
n is 1 to 10; preferably 1 to 6, more preferably 1 to 3.
m is 0 to 10, preferably 1 to 6, more preferably 1 to 3, and
the resulting dye forms a liquid-crystalline phase in solvent such as an aqueous media, including hydrophilic colloids, when dispersed as described herein. Protocol for determining the presence of liquid-crystalline phases is also described herein.
Another preferred embodiment of the invention comprises an imaging element containing a liquid crystal-forming dye of structural Formula I.
Still another preferred embodiment of the invention comprises a radiation-sensitive element, such as a photographic element, containing a liquid-crystal forming dye of structural Formula I.
Yet another preferred embodiment of the invention comprises a method of preparing a liquid-crystalline dye dispersion which comprises adding a dye of structural Formula I to an aqueous medium at a temperature of from about 2xc2x0 C. to about 100xc2x0 C. and agitating the mixture for about 5 minutes to about 48 hours.
This invention provides a merocyanine dye, useful as a filter dye or light-absorbing compound in an imaging element, and especially in a radiation-sensitive element, such as a photographic element, which when dispersed in an aqueous medium, for example aqueous gelatin, dissolves then spontaneously forms a lyotropic liquid-crystalline phase which constitutes an unusually well-ordered and thermodynamically stable dye state. A dye in the liquid-crystalline state often possesses a coated xcexmax which is substantially bathochromic or hypsochromic to that of its monomeric isotropic solution (non-liquid crystalline) state and exhibits exceptionally high covering power at its coating xcexmax. Further, the liquid-crystalline dye phase often exhibits sharp-cutting bathochromnic and/or hypsochromic spectral features absorbing strongly at its coating xcexmax, while absorbing comparatively little light at wavelengths just below or just above its absorbance maximum. Further, the liquid-crystalline dye phase often possesses an unusually narrow halfbandwidth. The dyes of this invention can be formulated for incorporation into a photographic element using, for example, conventional ball-mill or media-mill procedures for producing dye dispersions (SPD""s), or more simply as direct gelatin dispersions (DGD""s) for incorporation in a photographic element, as discussed more fully below. In the photographic element, dyes in the spontaneously-formed liquid-crystalline state exhibit little, if any tendency to wander, and upon processing many are substantially free of post-process stain problems.
As noted above, the dispersion of this invention comprises a liquid-crystal forming dye of Formula I:
[Dxe2x80x94(X)m]xe2x80x94(Y)n
wherein
D is a merocyanine dye.
Each Y contains an ionic or a nonionic solubilizing substituent or a group with a pKa value of less than 4 in water.
Each X is a nonionic substituent.
n is 1 to 10; preferably 1 to 6, more preferably 1 to 3.
m is 0 to 10, preferably 1 to 6, more preferably 1 to 3, and
the resulting dye forms a liquid-crystalline phase in solvent such as an aqueous media, including hydrophilic colloids, when dispersed as described herein. Protocol for determining the presence of dye liquid-crystalline phases is also described herein.
In Formula I, D represents a merocyanine dye residue. Useful dyes include those absorbing in the UV region (below 400 nm), the visible region (400-700 nm), and the infrared region (above 700 nm)
Each Y may independently be a group containing an ionic or nonionic solubilizing substituent or a group with a pKa in water of below 4, and each X may independently be a nonionic substituent, each X and Y being present in number and combination such that the resulting dye forms a liquid-crystalline phase when dispersed or dissolved in the desired solvent. For water-based solvent media, examples of solubilizing groups contained in Y include, but are not restricted to carboxylate (CO2xe2x88x92), sulfo (SO3xe2x88x92), sulfato (OSO3xe2x88x92), sulfate (SO4xe2x88x92), phosphate, phosphonate, trialkylammonium (R3N+), pyridinium, alkylpyridinium, hydroxylate (Oxe2x88x92), enolate (Cxe2x95x90Cxe2x80x94Oxe2x88x92), dicyanovinylate (Cxe2x95x90CCH(CN)2xe2x88x92), alkyl ethers such as (CH2OCH2OCH3), zwitterionic groups such as amino acids, phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine, and groups with a pKa value below 4 and preferably below 3.8 such as sulfonic acid, acylsulfonamide (CONHSO2R), saccarin moeities (cyclic acylsulfamdes), and sulfonylsulfonamido (SO2NHSO2R). Y or the solubilizing substituent contained in Y may be attached to the dye in any way; it may be attached directly to the chromophoric moeity itself, D, or to X or may be attached to the dye as part of a linking group such as a substituted or unsubstituted alkyl or aryl group. Examples of groups for X include, but are not restricted to aryl, alkyl, aralkyl, halogen, cycloalkyl, alkoxy, alkylamino, acyl, carboxy, carboxyalkyl, sulfonamido or alkylthio, and more preferably are phenyl, halogen, and benzo.
In a preferred embodiment of the invention the liquid-crystal forming dye of structural Formula I is a merocyanine of Formula II: 
wherein A is an activated methylene moeity or a ketomethylene moeity as described above, R1 is substituted or unsubstituted aryl, alkyl or aralkyl, R2 to R5 each individually represent hydrogen, alkyl, cycloalkyl, alkeneyl, substituted or unsubstituted aryl, heteroaryl or aralkyl, alkylthio, hydroxy, hydroxylate, alkoxy, amino, alkylamino, halogen, cyano, nitro, carboxy, acyl, alkoxycarbonyl, aminocarbonyl, sulfonamido, sulfamoyl, including the atoms required to form fused aromatic or heteroaromatic rings, or groups containing solubilizing substituents as described above for Y. L1 through L6 are substituted or unsubstituted methine groups, (including the possibility of any of them being members of a five or six-membered ring where at least one and preferably more than one of s, t, or v is 1 ), Y2 is O, S, Te, Se, NRx, or CRyRz (where Rx, Ry and Rz are alkyl groups with 1-5 carbons), and s and t and v are independently 0 or 1; with the proviso that at least one substituent on the dye of Formula II contains an ionic or non-ionic solubilizing group or a group with a pKa value less than 4 in water as described for Y in Formula I.
In a preferred embodiment, Y2 is O, S, N or C, and the sum of s, t and v is 1 or 2.
In another especially preferred embodiment the liquid-crystal forming dye of Formula I is a merocyanine dye of Formula III: 
wherein R6 is a substituted or unsubstituted aryl, heteroaryl, or a substituted or unsubstituted amino group; G1 is O or dicyanovinyl (NCCH2CN), E1 is an electron-withdrawing group, L8 to L13 represent methine groups as described above for L1 to L6, R1 to R5, Y2, and s, t and v are as described above; with the proviso that at least one substituent on the dye of Formula III is a ionic or non- ionic solubilizing group or a group with a pKa value less than 4 in water as described for Y in Formula I.
In a preferred embodiment, Y2 is O or S, E1 is cyano, R6 is a substituted or unsubstituted phenyl or heteroaromatic ring, R1 is sulfoalkyl and sum of s, t and v is 1 or 2. In an especially preferred embodiment, G1 is dicyanovinyl, E1 is cyano, and Y2 is O.
In an another preferred embodiment of the invention, the liquid-crystal forming dye of Formula I is a dye of Formula IV: 
wherein G2 is oxygen (O) or dicyanovinyl (NCCH2CN), R1 to R5 groups each individually represent groups as described above, and R7 through R10 represent groups as described above for R1 to R5, Y2, L8 through L13, and s, t and v are as described above, with the proviso that at least one substituent on the dye of Formula IV is a ionic or non-ionic solubilizing group or a group with a pKa value less than 4 in water as described for Y in Formula I.
In an another preferred embodiment of the invention, the liquid-crystal forming dye of Formula I is a dye of Formula V: 
wherein R12 groups each individually represent the-groups described for R2 through R5 above, Y3 represents O, S, NRx, or CRyRz (where Rx, Ry and Rz are alkyl groups with 1-5 carbons), R11 represents substituted or unsubstituted aryl, alkyl or acyl, x is 0, 1, 2, and Y2, R1, R2 through R5, L8 through L13, and s, t and v are as described above; with the proviso that at least one substituent on the dye of Formula V is a ionic or non-ionic solubilizing group or a group with a pKa value less than 4 in water as described for Y in Formula I. In a preferred embodiment Y2 and Y3 are O or S, R1 is sulfoalkyl, and the sum of s, t and v is 1 or 2.
In an another preferred embodiment of the invention, the liquid-crystal forming dye of Formula I is a dye of Formula VI: 
wherein E2 represents an electron-withdrawing group, preferably cyano, R11 represents substituted or unsubstituted aryl, alkyl or acyl, and Y2, R1, R2 through R5, L8 through L13, and, s, t and v are as described above; with the proviso that at least one substituent on the dye of Formula VI contains an ionic or non-ionic solubilizing group or a group with a pKa value less than 4 in water as described for Y in Formula I. In a preferred embodiment, E2 is cyano and R1 is sulfoalkyl.
In an another preferred embodiment of the invention, the liquid-crystal forming dye of Formula I is a dye of Formula VII: 
wherein R13 is a hydrogen, substituted or unsubstituted alkyl, aryl or aralkyl, R14 is substituted or unsubstituted alkyl, aryl or aralkyl, alkoxy, amino, acyl, alkoxycarbonyl, carboxy, carboxylate, cyano, or nitro; R1 to R5, L8-L13, Y2, and s, t and v are as described above; with the proviso that at least one substituent on the dye of Formula VII contains an ionic or non-ionic solubilizing group or a group with a pKa value less than 4 in water as described for Y in Formula I. In a preferred embodiment, R13 is an aryl group, and the sum of s, t and v is 1 or 2.
In an another preferred embodiment of the invention, the liquid-crystal forming dye of Formula I is a dye of Formula VIII: 
wherein R15 and R16 are each independently a hydrogen, substituted or unsubstituted alkyl, aryl or aralkyl, Y4 is O or S, R1 to R5, L8 to L13, Y2, and s, t and v are as described above; with the proviso that at least one substituent on the dye of Formula VIII contains an ionic or non-ionic solubilizing group or a group with a pKa value less than 4 in water as described for Y in Formula I. In a preferred embodiment the sum of s, t and v is 1 or 2.
Still another preferred embodiment of the invention comprises an imaging element containing a liquid crystal-forming dye of structural Formulae I-VIII.
Still another preferred embodiment of the invention comprises a radiation-sensitive element, such as a photographic element, containing a liquid-crystal forming dye of structural Formulae I-VIII.
In Formula II, activated methylene or ketometylene moieties represented by A are well known in the art and are described, for example, in Hamer, The Cyanine Dyes and Related Compounds, pages 469-494 and 595-604. In accordance with the present invention, preferred active methylene groups include, but are not restricted to those derived from benzoylacetonitrile, 2-pyrazolin-5-one, pyrazolidindione, tricyanopropene, barbituric acid, indanedione, dicyanovinylindanedione, bis(dicyanovinyl)indanedione, pyrrolinone, furanone (such as cyanophenylfuranone and derivatives) benzothiophene dioxide, dicyanovinylbenzothiophene dioxide, rhodanine, benzofuranone, chromandione, cyclohexanedione, isoxazolinone, pyrazolopyridine, pyridone and pyrandione, and any of these moieties may be optionally substituted with ionic or non-ionic solubilizing group(s) or an ionizable group with a pKa value less than 4 in water.
In the tables of this disclosure, M+ is a cation such as H+, Et3NH+, C5H5NH+, Na+, and K+, and Xxe2x88x92 is an anion such as Brxe2x80x94, Clxe2x80x94, and pTs-. xe2x80x9cGroupxe2x80x9d wherever used in the present application includes the possibility of being substituted or unsubstituted. E1 and E2 are electron-withdrawing substituents which are discussed in March, Advanced Organic Chemistry, pages 20-21, 228-229, 386-387 and 494-497. Groups for E1 and E2 may include cyano, acyl, benzoyl, phenacyl, aminocarbonyl, alkoxycarbonyl, aryl, nitro or arylsulfonyl or alkylsulfonyl.
The solubilizing group contained in Y may be chosen easily by one skilled in the art. Examples of ionic solubilizing groups include anionic groups such as carboxylate (CO2xe2x88x92), sulfo (SO3xe2x88x92), sulfato (OSO3xe2x88x92), sulfonate (SO4xe2x88x92), hydroxylate (Oxe2x88x92), enolate (Cxe2x95x90Cxe2x80x94Oxe2x88x92), dicyanovinylate (Cxe2x95x90Cxe2x80x94C(CN)2xe2x88x92), phosphate, and phosphonate, cationic groups such as ammonium, alkylammonium, dialkylammonium, trialkylammonium (alkyls may be substituted), and pyridinium, and zwitterionic groups such as amino acids, phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl serine. Examples of non-ionic solubilizing groups contained in Y include alkyl ethers such as (xe2x80x94O(CH2)nOCH3 or (CH2OCH2OCH3). Y may also contain an ionizable group with a pKa in water less than 4. Examples of ionizable groups with pKa values below 4 in water include sulfonic acid (SO3H), acylsulfomido (CONHSO2R), saccarhin (cyclic acylsulfonamide), sulfonylsulfonamido (SO2NHSO2R), dinitroalkyl, dinitrophenol, and activated carboxy moieties such as dichloroalkylcarboxy, and salicylic acid. In all structural descriptions, Y may be either an ionic or nonionic solubilizing group or group with a pKa value below 4, or Y may be a group containing one of these said solubilzing moeities.
The merocyanine dye residues represented by D in Formula I may be derived from suitable heterocyclic nuclei are of the type commonly used in senstizing dyes and are well known in the art. Many, for example, are described in Mees and James, Theory of The Photographic Process, 4th edition, pages 195-203. Useful heterocyclic nuclei include thiazole, selenazole, oxazole, telerozole, imidazole, indole, benzoxazole, benzothiazole, benzimidazole or benzindole, and more preferably a substituted or unsubstituted benzoxazole, benzothiazole, benzimidazole or benzindole nucleus.
Any L group may be substituted or unsubstituted. This includes the possibility that any of them may be members of a 5 or 6-memebered ring. In Formulae II to VIII preferred substituents for R2 to R5 include groups such as phenyl, benzo (fused phenyl), halogen (especially chloro, fluoro, bromo), and pyrrole.
Methine groups may be substituted with, for example, an alkyl, alkenyl, aryl, aralkyl, cycloalkyl, or heterocyclic group or, as mentioned above, if more than one of p, q, or r is 1, two or more methine groups together with their substituents may form a 5- or 6-membered carbocyclic or heterocycllic ring.
In general, when reference in this application is made to a particular moiety or group it is to be understood that such reference encompasses that moiety whether unsubstituted or substituted with one or more substituents (up to the maximum possible number). For example, xe2x80x9calkylxe2x80x9d or xe2x80x9calkyl groupxe2x80x9d refers to a substituted or unsubstituted alkyl, while xe2x80x9cbenzene groupxe2x80x9d refers to a substituted or unsubstituted benzene (with up to six substituents). Generally, unless otherwise specifically stated, substituent groups usable on molecules herein include any groups, whether substituted or unsubstituted, which do not destroy properties necessary for the photographic utility. Examples of substituents on any of the mentioned groups can include known substituents, such as: halogen, for example, chloro, fluoro, bromo, iodo; hydroxy; alkoxy, particularly those xe2x80x9clower alkylxe2x80x9d (that is, with 1 to 6 carbon atoms, for example, methoxy, ethoxy; substituted or unsubstituted alkyl, particularly lower alkyl (for example, methyl, trifluoromethyl); thioalkyl (for example, methylthio or ethylthio), particularly either of those with 1 to 6 carbon atoms; substituted or unsubstituted alkenyl, preferably of 2 to 10 carbon atoms (for example, ethenyl, propenyl, or butenyl); substituted and unsubstituted aryl, particularly those having from 6 to 20 carbon atoms (for example, phenyl); and substituted or unsubstituted heteroaryl, particularly those having a 5 or 6-membered ring containing 1 to 3 heteroatoms selected from N, O, or S (for example, pyridyl, thienyl, furyl, pyrrolyl); acid or acid salt groups such as any of those described below; hydroxylate, amino, alkylamino, cyano, nitro, carboxy, carboxylate, acyl, alkoxycarbonyl, aminocarbonyl, sulfonamido, sulfamoyl, sulfo, sulfonate, alkylammonium, and an ionizable group with a pKa value below 4 in water; and others known in the art. Alkyl substituents may specifically include xe2x80x9clower alkylxe2x80x9d (that is, having 1-6 carbon atoms), for example, methyl, ethyl, and the like. Further, with regard to any alkyl group or alkylene group, it will be understood that these can be branched or unbranched and include ring structures.
Examples of preferred dyes of the invention are listed below.

The dyes of Formulae I-VIII can be prepared by synthetic techniques well-known in the art, as illustrated by the synthetic examples below. Such techniques are further illustrated, for example, in xe2x80x9cThe Cyanine Dyes and Related Compoundsxe2x80x9d, Frances Hamer, Interscience Publishers, 1964.
The liquid-crystalline dye dispersions of this invention may be prepared by well-known methods commonly employed for preparing solid particle dye dispersions. Here, a slurry of the dye in an aqueous medium comprising water and a surfactant or water-soluble polymer is subjected to a milling procedure such as ball-milling, sand-milling, media-milling or colloid-milling (preferably media-milling). The dye slurry can then be mixed with aqueous gelatin at an appropriate concentration (preferablyxe2x89xa630% w/w) and at a temperature (preferably 20 to 90xc2x0 C.)for use in a photographic element.
In another preferred embodiment, the liquid-crystalline dye dispersions of this invention may be prepared using a direct gelatin dispersion (DGD) method wherein the finely powdered dye or aqueous slurry thereof is simply mixed or agitated with water or with an aqueous medium containing gelatin (or other hydrophilic colloid) at an appropriate concentration (preferably xe2x89xa630% w/w) and at a temperature (preferably 0 to 100xc2x0 C.).
In either of the preferred methods, the dyes may be subjected to elevated temperatures before and/or after gelatin dispersion, but to obtain desirable results, this heat treatment is carried out preferably after dispersing in gelatin. The optimal temperature range for preparing gelatin-based dispersions is 20xc2x0 C.-100xc2x0 C., depending on the concentration of the gelatin, but should remain below the decomposition points of the dyes, and, preferably forth range of 5 minutes to 48 hours. A similar heat treatment may be applied, if so desired, to dyes prepared by milling methods as solid particle dispersions before and/or after dispersion in aqueous gelatin to obtain effective results. Furthermore, if so desired, pH and/or ionic strength and solvent composition adjustments, for example, may be utilized to control the solubility and liquid crystal-forming properties of dyes prepared using SPD or DGD formulation techniques. The direct gelatin dispersion method is advantageous in that it does not necessarily require the use of organic solvents, surfactants, polymer additives, electrolytes, milling processes, pH control or the like. It is generally simpler, faster, more forgiving and more flexible than milling processes. A related method described by Boettcher for preparing concentrated sensitizing dye dispersions in aqueous gelatin (PCT WO 93/23792) is equally effective when applied to the inventive dyes. The entire disclosure of WO 93/23792 is incorporated herein by reference. The inventive lyotropic liquid-crystalline dye dispersions may be incorporated directly into imaging elements.
Solid particle dispersion and direct gelatin dispersion formulations of the compound of Formula (I-VIII) are useful as general purpose filter dyes, alone or in combination with other filter dyes in photographic elements. The dyes formulated as described above possess a pronounced tendency to form liquid crystal phases spontaneously at a variety of pH""s, including typical coating pH""s of 6 or less (generally 4-6) such that they do not substantially wander from the layer in which they are coated. However, they are highly soluble at processing pH""s of 8 or more (generally 8-12), such that they are often still fully removed during photographic processing.
Our invention comprises a wide variety of dye classes which are functionalized to form liquid crystalline phases in solvents, especially water, and hydrophilic colloids such as aqueous gelatin. These materials would be especially useful as filter dyes in photographic systems as described above, as spectral sensitizers, and in non-photographic imaging applications such as inkjet, barcoding, and thermally-developed imaging systems.
There are few teachings addressing dye lyotropic liquid-crystalline phases. Additionally, no teachings are provided that would enable one skilled in the art to design and synthesize dyes capable of forming liquid crystals or to influence their formation in imaging elements.
For most materials, it is generally accepted that only three states of matter exist; namely, solids, liquids and gases. However, some materials exhibit a fourth state of matter commonly referred to as a liquid crystal phase (or mesophase). Liquid crystal phases are neither crystalline solids nor isotropic liquids, but exhibit some of the characteristics of both. A liquid crystal phase can be described simply as being a liquid with a certain degree of molecular order. As described below, this molecular order gives rise to measurable anisotropy in the bulk properties of a material that is otherwise much like a liquid. Consequently, the physical properties of liquid-crystalline materials are unique and distinct from those of solids and liquids. These differences can be utilized to advantage in the formulation of photographic elements and also allow detection of the liquid crystal phase by a variety of optical and spectroscopic techniques.
Liquid crystals can be classified as thermotropic or lyotropic. The dye compositions of the current invention are of the lyotropic type, however, for puposes of comparision, we first give a brief description the thermotropic type: Some crystalline compounds do not yield an isotropic liquid immediately upon melting, instead, the newly formed xe2x80x9cmeltxe2x80x9d is a liquid crystal phase (mesophase). In the simple cases, further heating results in the formation of an ordinary isotropic liquid. The phase that exists above the melting point of the crystalline solid but below the formation temperature for the isotropic liquid is known as a thermotropic liquid crystal phase. In some cases, heating the initally formed mesophase does not result in an isotropic liquid, but rather, to one or more intermediate liquid crystal phases, and finally, the last formed of these, upon further heating, yields the isotropic liquid. All of the mesophases formed in this way are conventionally classified as thermotropic. The term thermotropic liquid crystal is also extended to include eutectic mixtures of compounds. Thermotropic liquid crystals are generally colorless organic materials and are typically hydrophobic (water-insoluble) in character. They are commonly employed in electro-optical display devices, for example digital watches and calculators.
In contrast, spontaneous formation of lyotropic liquid crystals can be achieved at a fixed temperature by simple addition of a solvent to a suitable solute (mesogen). The solvent is typically (but not necessarily) water and lyotropic mesophases are stable over finite ranges of both concentration and temperature. Typical lyotropic mesogens are amphiphilic. The term amphiphilic acknowledges that both hydrophobic groups (e.g. aliphatic, aromatic, etc.) and hydrophilic groups (e.g. CO2xe2x88x92M+, SO3+M+, SO4xe2x88x92M+, O(CH2CH2O)x etc.) are present on the same molecule. Examples include, surfactants, lipids, polymers, dyes, and drugs. The amphiphilic nature and the specific hydrophilic-hydrophobic balance (HHB) of these molecules influences their tendency to form lyotropic mesophases.
The structural type(s) and stability with respect to concentration and temperature of the liquid crystalline phase(s) formed are highly mesogen-dependent. For example, Koll et al. (U.S. Pat. No. 4,309,183, Jan. 5, 1982) teach how a lyotropic liquid-crystalline phase of a particular anionic azo reactive dyestuff can be prepared in water at room temperature and dye concentrations of 12-35%, for the specific use of dyeing and printing natural and synthetic substrates. However, no reference to such dyes for use in imaging elements has been reported.
Because of the complex interplay of short-range inter-molecular and long-range inter-aggregate forces controlling lyotropic mesophase formation, in general it is difficult to predict the likelihood or stability of liquid crystal formation for any given solute-solvent combination.
It is part of the purpose of this invention to demonstrate that a wide variety of chromophores can and do form lyotropic liquid crystals upon suitable manipulation of substituents. It is a further purpose of this work to provide some examples of substituent combinations that are effective in transforming some quite ordinary dyes classes, that is to say, dye classes for which mesophases have never been reported, into photographically useful lyotropic mesogens.
In the preferred embodiment, the amphiphilic filter dye will form any liquid-crystalline phase upon dispersing said dye in the hydrophilic solvent medium, typically, but not limited to, water or aqueous gelatin, at the wet laydown (dye concentration) and temperature of choice (preferably xe2x96xa1 30% w/w dye, more preferably xe2x89xa610% w/w dye, even more preferably xe2x89xa65% w/w dye and most preferably xe2x89xa60.5% w/w dye, between 0xc2x0 C. and 100xc2x0 C.). In the most preferred embodiment, said dye mesophase will possess a layered smectic structure, and in another preferred embodiment the dye mesophase will possess a nematic or hexagonal structure. We have discovered that the liquid-crystalline phase stability of lyotropic amphiphilic (particularly ionic) filter dyes may also be sensitive to the presence of addenda such as gelatin of different types, polymers, organic solvents (such as alcohols, acetone etc.) and surfactants. For example, low-levels of common electrolytes can stabilize ionic dye mesophase formation. Enhanced mesophase stability of ionic filter dyes (with respect to both temperature and concentration) may be realized simply by the judicious choice of photographic gelatin (e.g. so-called regular, deionized or decalcified gelatin grades) which contain different levels and types of electrolyte cations and anions (e.g. calcium, magnesium, sodium, chloride, sulphate etc.) as a by-product of gelatin manufacture. Similarly, the use of non-deionized water or the addition of low salt levels to purified (deionized or distilled) water, can afford enhanced mesophase stability for certain ionic filter dyes. The preferred dyes of this invention are chosen to exhibit stable lyotropic mesophases under the practical conditions generally employed for their formulation, dispersion, coating and drying. It is understood that someone skilled in the art of dyes could, with the guidance provided in this disclosure, systematically optimize dye structure and/or solvent conditions to enhance and control dye mesophase formation and stability for a suitable mesogen-solvent combination.
Since mesophase formation is both concentration and temperature dependent, it is understood that some of the preferred amphiphilic filter dyes may initially form an isotropic solution phase which will undergo a transition to a more concentrated and thermally-stable mesophase during the drying process (thermal stability of dye mesophases invariably increases with dye mesophase concentration).
Some of the preferred amphiphilic filter dyes initially dispersed in the wet hydrophilic colloid medium (e.g. aqueous gelatin) as a dilute liquid-crystalline dye phase, may remain wholly liquid-crystalline upon drying or undergo a (for example, concentration-dependent or ionic strength-dependent) reversible transition from the liquid-crystalline state to a crystalline, semi-crystalline, or amorphous solid dye state, or a mixture thereof, during the drying process. However, we have found that in such instances the preferred dyes still largely retain the useful spectral and physical properties associated with the originally dispersed dilute dye mesophase (e.g. absorption envelope providing good covering power, layer specificity, incubation stability, rapid processing elution and or bleachability). The final physical form of the gelatin-dispersed dye (liquid-crystalline, crystalline, amorphous solid) will depend on the precise phase behaviour of said dye in relation to the retained moisture (water) content of the evaporated (dried-down) gelatin film under given conditions of temperature and humidity and the presence of other solutes. However, according to the invention, dyes which remain liquid crystalline when formulated and dispersed in the photographic vehicle, or those which pass through a transitory liquid-crystalline phase at any stage during the subsequent coating and drying process, will afford the useful and unique combination of both spectral and physical properties, described herein. It should be emphasized that reference in this disclosure to xe2x80x9cevaporatedxe2x80x9d or xe2x80x9cdriedxe2x80x9d coatings refers to coatings of wet aqueous gelatin melts from which excess water or solvent has been allowed to evaporate or has been removed by drying processes, but which still retain an equilibrium moisture level typical of finished imaging elements especially photographic imaging elements.
According to the invention, the preferred dye chromophores must possess some added degree of hydrophilicity, imparted by ionic, zwitterionic or nonionic solubilizing groups, to be capable of forming lyotropic liquid-crystalline phases in aqueous-based media. Similarly, if so desired, for non-aqueous (e.g. organic) solvent applications, the dye should possess additional hydrophobic, rather than hydrophilic, solubilizing moieties, such as branched aliphatic chains.
Common mesophase structural types, such as layered smectic (e.g. lamellar), columnar hexagonal and nematic, which possess varying degrees of orientational and translational molecular order, may be formed by many diverse and disparate lyotropic mesogens. Because of the inherent ordered nature of these anisotropic, thermodynamically stable, supramolecular structures, experimental techniques including, for example, small-angle X-ray (or neutron) scattering, polarized-light optical microscopy and quadrupole (e.g. 23Na, 2H, 17O, 14N etc.) NMR spectroscopy may be routinely applied to identifying and characterizing the structure and physico-chemical properties of lyotropic mesophases.
According to the invention, the preferred dyes can be readily identified using the technique of polarized-light optical microscopy (as described by N. H. Hartshorne in, xe2x80x9cThe Microscopy of Liquid Crystalsxe2x80x9d, Microscope Publications Ltd., London, England, 1974). In order to ascertain the exact quantitative mesophase behavior of a given dye-solvent combination, a range of sample mixtures of known composition are prepared (typically dyes dissolved in aqueous gelatin) and viewed in polarized light as wet thin films (contained within sealed glass capillary cells of known pathlength) and slowly-evaporated thin films (hand-coated onto glass microscope slides and air-dried) to establish the precise concentration and temperature ranges of dye mesophase stability. These same thin-film preparations may also be used to elucidate and quantify the spectral absorption properties of the dye mesophase, such as absorption wavelength, bandwidth, extinction coefficient etc. using a uv-vis spectrophotometer.
Simple observations of the characteristic birefringent type-textures and rheology (flow behavior under shear) displayed by thin-film mesophase preparations in polarized light are usually sufficient to establish the mesophase structural type (e.g. smectic, nematic, hexagonal depending upon the specific long-range inter-aggregate ordering) as a function of solute-solvent concentration and temperature. Dyes forming lyotropic chromonic nematic mesophases may be identified from a range of fluid, viscoelastic textures including so-called Schlieren, Tiger-Skin, Reticulated, Homogeneous (Planar), Thread-like, Droplet and Homeotropic (Pseudoisotropic). Lyotropic chromonic hexagonal mesophases usually display viscous, birefringent Herringbone, Ribbon or Fan-like textures while lyotropic chromonic smectic mesophases may display Grainy-Mosaic, Frond-like (Pseudo-Schlieren), Spherulitic and Oily-Streak birefringent textures. In some cases where the liquid-crystalline nature of the sample cannot be established unequivocally using polarized-light optical microscopy other well-established experimental techniques may be utilized. For example, lyotropic mesophases exhibit characteristic quadrupole NMR spectroscopy lineshapes and quadrupole splittings, while small-angle and wide-angle X-ray (or neutron) diffraction measurements provide unique and characteristic structured diffraction patterns (refer to xe2x80x9cLiquid Crystals and Plastic Crystalsxe2x80x9d, eds. G. W. Gray and P. A. Winsor, Ellis Horwood Ltd., Chichester, UK, 1974, Vols.1 and 2). Such phase-dependent properties may be used to differentiate, for example, a liquid-crystalline filter dye dispersion from a conventional microcrystalline (i.e.solid) filter dye dispersion.
A particular advantage of the inventive dyes is that in the liquid crystalline state, they provide higher covering power at their coating xcexmax than comparable known dyes which are insoluble and exist as microcrystalline solid particles in the photographic medium. This advantage is particularly important in modem film formats and processing conditions, as filter dyes with high covering power need not be coated at as high a coverage as dyes with lower covering power in order to achieve the same degree of light filtration. In addition to reducing manufacturing costs, lower levels of coated dyes will reduce the level of unwanted dye stain in the processed photographic element, and will reduce the level of dye residue built up in the processing solutions, and the resulting lower levels of dissolved dye residue removed from photographic elements will have reduced environmental impact.
A further advantage of dyes of the invention is that they generally possess absorbance envelopes that are sharper cutting on the bathochromic side than typical solid particle dyes. This feature is especially advantageous when strong light absorbance is required in a spectral region up to a specific xcexmax and maximum light transmission is required past the specifiedxcexmax. Such filter or trimmer dyes are especially useful when coated in specific layers of color photographic films to effectively prevent light of a specific wavelength region from exposing radiation-sensitive layers below the light filtration layer containing the dye, but without causing speed losses in the layer below the filter dye. A green filter dye coated directly above a red-sensitive silver halide layer is a particularly advantageous example of such absorbance features, and excellent green/red speed separation can be realized. A sharp-cutting bathochromic edge on a filter or trimmer dye enables excellent color reproduction with minimum speed loss by absorbing light efficiently up to its absorbance maximum, but very little if any just past its absorbance maximum. A magenta trimmer dye (green absorber) which is only moderately sharp-cutting on the bathochromic edge may function adequately as a filter dye, but its unwanted absorbance in the red region past its xcexmax will rob the red-sensitive emulsion coated below it of red light and hence speed. In a typical color photographic element, it is desirable to have a green-absorbing filter dye which when coated absorbs strongly at wavelengths close to 550 nm, but which absorbs comparatively little at wavelengths greater than 550 nm. It should be emphasized that the exact envelope of desirable light absorbance for a filter dye, even specifically a green filter dye, varies tremendously from one photographic element to another depending on the intended purpose of the material. Some photographic elements might require a filter dye, such as a green filter dye, which absorbs strongly up to a wavelength somewhat shorter or longer than 550 nm, but is sharp cutting on the bathochromic side, mostly transmitting wavelengths of light past the desired absorbance xcexmax. The feature of coated dye absorbance exhibiting a sharp cutting bathochromic and/or hypsochromic characteristic is fundamentally useful for wavelength-specific light filtration, though the exact wavelength of desired spectral shift from absorbance to transmission may be different for different photographic materials.
A further advantage of the dyes of the invention is that in the liquid crystalline state, many are much sharper absorbing than in their dissolved isotropic solution state, that is, they possess a much narrower halfbandwidth. Furthermore, unlike a dye in the dissolved, isotropic solution state, the dye in the liquid-crystalline state is essentially immobile and not prone to gross diffusion and thus can be coated layer specifically.
The dyes may be located in any layer of the element where it is desirable to absorb light, but in photographic elements it is particularly advantageous to locate them in a layer where they will be solubilized and washed out during processing. Useful amounts of dye range from 1 to 1000 mg/m2. The dye should be present in an amount sufficient to yield an optical density at the absorbance Dmax in the spectral region of interest before processing of at least 0.10 density units and preferably at least 0.50 density units. This optical density will generally be less than 5.0 density units for most photographic applications.
The dyes of the invention can be used as interlayer dyes, trimmer dyes, antihalation dyes or light-absorbing elements. They can be used to prevent crossover in X-ray materials as disclosed in U.S. Pat. Nos. 4,900,652 and 4,803,150 and European Patent Application Publication No. 0 391 405, to prevent unwanted light from reaching a sensitive emulsion layer of a multicolor photographic element as disclosed in U.S. Pat No. 4,988,611, and for other uses as indicated by the absorbance spectrum of the particular dye. The dyes can be used in a separate filter layer or as an intergrain absorber.
The liquid crystal-forming dyes of Formula (I-XIII) are useful for the preparation of radiation sensitive materials. Such materials are sensitive to radiation such as visible light, ultraviolet, infrared, or X-ray.
The liquid crystal-forming dyes of Formula (I-VIII) are also useful in non-photographic imaging elements such as thermally-developable elements, or as dye materials for inkjet applications. The non-photographic imaging material may be an optical recording medium, such as a CD or other medium sensitive to a laser, light-emitting diode, or a thermally-developable material. Another aspect of this invention comprises a radiation sensitive element containing a liquid crystal-forming dye of Formula (I-VIII). Preferably, the radiation sensitive element is a photographic element comprising a support bearing at least one light sensitive hydrophilic colloid layer and at least one other hydrophilic colloid layer. A dye of Formula I-VIII may be incorporated in a hydrophilic layer of the photographic element in any known way.
The support of the element of the invention can be any of a number of well-known supports for photographic elements as discussed more fully below.
The photographic elements made by the method of the present invention can be single color elements or multicolor elements. Multicolor elements contain dye image-forming units sensitive to each of the three primary regions of the spectrum. Each unit can be comprised of a single emulsion layer or of multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer.
A typical multicolor photographic element comprises a support bearing a cyan dye image-forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler. The element can contain additional layers, such as filter layers, interlayers, overcoat layers, subbing layers, and the like. All of these can be coated on a support which can be transparent or reflective (for example, a paper support).
Photographic elements of the present invention may also usefully include a magnetic recording material as described in Research Disclosure, Item 34390, November 1992, or a transparent magnetic recording layer such as a layer containing magnetic particles on the underside of a transparent support as in U.S. Pat. Nos. 4,279,945 and 4,302,523. The element typically will have a total thickness (excluding the support) of from 5 to 30 microns. While the order of the color sensitive layers can be varied, they will normally be red-sensitive, green-sensitive and blue-sensitive, in that order on a transparent support, (that is, blue sensitive furthest from the support) and the reverse order on a reflective support being typical.
The present invention also contemplates the use of photographic elements of the present invention in what are often referred to as single use cameras (or xe2x80x9cfilm with lensxe2x80x9d units). These cameras are sold with film preloaded in them and the entire camera is returned to a processor with the exposed film remaining inside the camera. Such cameras may have glass or plastic lenses through which the photographic element is exposed.
In the following discussion of suitable materials for use in elements of this invention, reference will be made to Research Disclosure, September 1996, Number 389, Item 38957, which will be identified hereafter by the term xe2x80x9cResearch Disclosure I.xe2x80x9d The Sections hereafter referred to are Sections of the Research Disclosure I unless otherwise indicated. All Research Disclosures referenced are published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire P010 7DQ, ENGLAND. The foregoing references and all other references cited in this application, are incorporated herein by reference.
The silver halide emulsions employed in the photographic elements of the present invention may be negative-working, such as surface-sensitive emulsions or unfogged internal latent image forming emulsions, or positive working emulsions of internal latent image forming emulsions (that are either fogged in the element or fogged during processing). Suitable emulsions and their preparation as well as methods of chemical and spectral sensitization are described in Sections I through V. Color materials and development modifiers are described in Sections V through XX. Vehicles which can be used in the photographic elements are described in Section II, and various additives such as brighteners, antifoggants, stabilizers, light absorbing and scattering materials, hardeners, coating aids, plasticizers, lubricants and matting agents are described, for example, in Sections VI through XIII. Manufacturing methods are described in all of the sections, layer arrangements particularly in Section XI, exposure alternatives in Section XVI, and processing methods and agents in Sections XIX and XX.
With negative working silver halide a negative image can be formed. Optionally a positive (or reversal) image can be formed although a negative image is typically first formed.
The photographic elements of the present invention may also use colored couplers (e.g., to adjust levels of interlayer correction) and masking couplers such as those described in EP 213 490; Japanese Published Application 58-172,647; U.S. Pat. No. 2,983,608; German Application DE 2,706,117C; U.K. Patent 1,530,272; Japanese Application A-1 13935; U.S. Pat. No. 4,070,191 and German Application DE 2,643,965. The masking couplers may be shifted or blocked.
The photographic elements may also contain materials that accelerate or otherwise modify the processing steps of bleaching or fixing to improve the quality of the image. Bleach accelerators described in EP 193 389; EP 301 477; U.S. Pat. Nos. 4,163,669; 4,865,956; and 4,923,784 are particularly useful. Also contemplated is the use of nucleating agents, development accelerators or their precursors (UK Patent 2,097,140; U.K. Patent 2,131,188); electron transfer agents (U.S. Pat. Nos. 4,859,578; 4,912,025); antifogging and anti color-mixing agents such as derivatives of hydroquinones, aminophenols, amines, gallic acid; catechol; ascorbic acid; hydrazides; sulfonamidophenols; and non color-forming couplers.
The elements may also contain filter dye layers comprising colloidal silver sol or yellow and/or magenta filter dyes and/or antihalation dyes (particularly in an undercoat beneath all light sensitive layers or in the side of the support opposite that on which all light sensitive layers are located) formulated either as oil-in-water dispersions, latex dispersions, solid particle dispersions, or as direct gelatin dispersions. Additionally, they may be used with xe2x80x9csmearingxe2x80x9d couplers (e.g., as described in U.S. Pat. No. 4,366,237; EP 096 570; U.S. Pat. Nos. 4,420,556; and 4,543,323.) Also, the couplers may be blocked or coated in protected form as described, for example, in Japanese Application 61/258,249 or U.S. Pat. No. 5,019,492.
The photographic elements may further contain other image-modifying compounds such as xe2x80x9cDeveloper Inhibitor-Releasingxe2x80x9d compounds (DIR""s). Useful additional DIR""s for elements of the present invention, are known in the art and examples are described in U.S. Patent Nos. 3,137,578; 3,148,022; 3,148,062; 3,227,554; 3,384,657; 3,379,529; 3,615,506; 3,617,291; 3,620,746; 3,701,783; 3,733,201; 4,049,455; 4,095,984; 4,126,459; 4,149,886; 4,150,228; 4,211,562; 4,248,962; 4,259,437; 4,362,878; 4,409,323; 4,477,563; 4,782,012; 4,962,018; 4,500,634; 4,579,816; 4,607,004; 4,618,571; 4,678,739; 4,746,600; 4,746,601; 4,791,049; 4,857,447; 4,865,959; 4,880,342; 4,886,736; 4,937,179; 4,946,767; 4,948,716; 4,952,485; 4,956,269; 4,959,299; 4,966,835; 4,985,336 as well as in patent publications GB 1,560,240; GB 2,007,662; GB 2,032,914; GB 2,099,167; DE 2,842,063, DE 2,937,127; DE 3,636,824; DE 3,644,416 as well as the following European Patent Publications: 272,573; 335,319; 336,411; 346, 899; 362, 870; 365,252; 365,346; 373,382; 376,212; 377,463; 378,236; 384,670; 396,486; 401,612; 401,613.
DIR compounds are also disclosed in xe2x80x9cDeveloper-Inhibitor-Releasing (DIR) Couplers for Color Photography,xe2x80x9d C. R. Barr, J. R. Thirtle and P. W. Vittum in Photographic Science and Engineering, Vol. 13, p. 174 (1969), incorporated herein by reference.
It is also contemplated that the concepts of the present invention may be employed to obtain reflection color prints as described in Research Disclosure, November 1979, Item 18716, available from Kenneth Mason Publications, Ltd, Dudley Annex, 12a North Street, Emsworth, Hampshire P0101 7DQ, England, incorporated herein by reference. The emulsions and materials to form elements of the present invention, may be coated on pH adjusted support as described in U.S. Pat. No. 4,917,994; with epoxy solvents (EP 0 164 961); with additional stabilizers (as described, for example, in U.S. Pat. Nos. 4,346,165; 4,540,653 and 4,906,559); with ballasted chelating agents such as those in U.S. Pat. No. 4,994,359 to reduce sensitivity to polyvalent cations such as calcium; and with stain reducing compounds such as described in U.S. Pat. Nos. 5,068,171 and 5,096,805. Other compounds useful in the elements of the invention are disclosed in Japanese Published Applications 83-09,959; 83-62,586; 90-072,629, 90-072,630; 90-072,632; 90-072,633; 90-072,634; 90-077,822; 90-078,229; 90-078,230; 90-079,336; 90-079,338; 90-079,690; 90-079,691; 90-080,487; 90-080,489; 90-080,490; 90-080,491; 90-080,492; 90-080,494; 90-085,928; 90-086,669; 90-086,670; 90-087,361; 90-087,362; 90-087,363; 90-087,364; 90-088,096; 90-088,097; 90-093,662; 90-093,663; 90-093,664; 90-093,665; 90-093,666; 90-093,668; 90-094,055; 90-094,056; 90-101,937; 90-103,409; 90-151,577.
The silver halide used in the photographic elements may be silver iodobromide, silver bromide, silver chloride, silver chlorobromide, silver chloroiodobromide, and the like. For example, the silver halide used in the photographic elements of the present invention may contain at least 90% silver chloride or more (for example, at least 95%, 98%, 99% or 100% silver chloride). In the case of such high chloride silver halide emulsions, some silver bromide may be present but typically substantially no silver iodide. Substantially no silver iodide means the iodide concentration would be no more than 1%, and preferably less than 0.5 or 0.1%. In particular, in such a case the possibility is also contemplated that the silver chloride could be treated with a bromide source to increase its sensitivity, although the bulk concentration of bromide in the resulting emulsion will typically be no more than about 2 to 2.5% and preferably between about 0.6 to 1.2% (the remainder being silver chloride). The foregoing % figures are mole %.
The type of silver halide grains preferably include polymorphic, cubic, and octahedral. The grain size of the silver halide may have any distribution known to be useful in photographic compositions, and may be either polydipersed or monodispersed.
Tabular grain silver halide emulsions may also be used. Tabular grains are those with two parallel major faces each clearly larger than any remaining grain face and tabular grain emulsions are those in which the tabular grains account for at least 30 percent, more typically at least 50 percent, preferably  greater than 70 percent and optimally  greater than 90 percent of total grain projected area. The tabular grains can account for substantially all ( greater than 97 percent) of total grain projected area. The tabular grain emulsions can be high aspect ratio tabular grain emulsionsxe2x80x94i.e., ECD/t greater than 8, where ECD is the diameter of a circle having an area equal to grain projected area and t is tabular grain thickness; intermediate aspect ratio tabular grain emulsionsxe2x80x94i.e., ECD/t=5 to 8; or low aspect ratio tabular grain emulsionsxe2x80x94i.e., ECD/t=2 to 5. The emulsions typically exhibit high tabularity (T), where T (i.e., ECD/t2) greater than 25 and ECD and t are both measured in micrometers (mm). The tabular grains can be of any thickness compatible with achieving an aim average aspect ratio and/or average tabularity of the tabular grain emulsion. Preferably the tabular grains satisfying projected area requirements are those having thicknesses of  less than 0.3 mm, thin ( less than 0.2 mm) tabular grains being specifically preferred and ultrathin ( less than 0.07 mm) tabular grains being contemplated for maximum tabular grain performance enhancements. When the native blue absorption of iodohalide tabular grains is relied upon for blue speed, thicker tabular grains, typically up to 0.5 mm in thickness, are contemplated.
High iodide tabular grain emulsions are illustrated by House U.S. Pat. No. 4,490,458, Maskasky U.S. Pat. No. 4,459,353 and Yagi et al EPO 0 410 410.
Tabular grains formed of silver halide(s) that form a face centered cubic (rock salt type) crystal lattice structure can have either {100} or {111} major faces. Emulsions containing {111} major face tabular grains, including those with controlled grain dispersities, halide distributions, twin plane spacing, edge structures and grain dislocations as well as adsorbed {111} grain face stabilizers, are illustrated in those references cited in Research Disclosure I, Section I.B.(3) (page 503).
The silver halide grains to be used in the invention may be prepared according to methods known in the art, such as those described in Research Disclosure I and James, The Theory of the Photographic Process. These include methods such as ammoniacal emulsion making, neutral or acidic emulsion making, and others known in the art. These methods generally involve mixing a water soluble silver salt with a water soluble halide salt in the presence of a protective colloid, and controlling the temperature, pAg, pH values, etc, at suitable values during formation of the silver halide by precipitation.
The silver halide to be used in the invention may be advantageously subjected to chemical sensitization with noble metal (for example, gold) sensitizers, middle chalcogen (for example, sulfur) sensitizers, reduction sensitizers and others known in the art. Compounds and techniques useful for chemical sensitization of silver halide are known in the art and described in Research Disclosure I and the references cited therein.
The photographic elements of the present invention, as is typical, provide the silver halide in the form of an emulsion. Photographic emulsions generally include a vehicle for coating the emulsion as a layer of a photographic element. Useful vehicles include both naturally occurring substances such as proteins, protein derivatives, cellulose derivatives (e.g., cellulose esters), gelatin (e.g., alkali-treated gelatin such as cattle bone or hide gelatin, or acid treated gelatin such as pigskin gelatin), gelatin derivatives (e.g., acetylated gelatin, phthalated gelatin, and the like), and others as described in Research Disclosure I. Also useful as vehicles or vehicle extenders are hydrophilic water-permeable colloids. These include synthetic polymeric peptizers, carriers, and/or binders such as poly(vinyl alcohol), poly(vinyl lactams), acrylamide polymers, polyvinyl acetals, polymers of alkyl and sulfoalkyl acrylates and methacrylates, hydrolyzed polyvinyl acetates, polyamides, polyvinyl pyridine, methacrylamide copolymers, and the like, as described in Research Disclosure I. The vehicle can be present in the emulsion in any amount useful in photographic emulsions. The emulsion can also include any of the addenda known to be useful in photographic emulsions. These include chemical sensitizers, such as active gelatin, sulfur, selenium, tellurium, gold, platinum, palladium, iridium, osmium, rhenium, phosphorous, or combinations thereof. Chemical sensitization is generally carried out at pAg levels of from 5 to 10, pH levels of from 5 to 8, and temperatures of from 30 to 80xc2x0 C., as described in Research Disclosure I, Section IV (pages 510-511) and the references cited therein.
The silver halide may be sensitized by sensitizing dyes by any method known in the art, such as described in Research Disclosure I. The dye may be added to an emulsion of the silver halide grains and a hydrophilic colloid at any time prior to (e.g., during or after chemical sensitization) or simultaneous with the coating of the emulsion on a photographic element. The dyes may, for example, be added as a solution in water or an alcohol. The dye/silver halide emulsion may be mixed with a dispersion of color image-forming coupler immediately before coating or in advance of coating (for example, 2 hours).
Photographic elements of the present invention are preferably imagewise exposed using any of the known techniques, including those described in Research Disclosure I, section XVI. This typically involves exposure to light in the visible region of the spectrum, and typically such exposure is of a live image through a lens, although exposure can also be exposure to a stored image (such as a computer stored image) by means of light emitting devices (such as light emitting diodes, CRT and the like).
Photographic elements comprising the composition of the invention can be processed in any of a number of well-known photographic processes utilizing any of a number of well-known processing compositions, described, for example, in Research Disclosure I, or in T. H. James, editor, The Theory of the Photographic Process, 4th Edition, Macmillan, New York, 1977. In the case of processing a negative working element, the element is treated with a color developer (that is one which will form the colored image dyes with the color couplers), and then with a oxidizer and a solvent to remove silver and silver halide. In the case of processing a reversal color element, the element is first treated with a black and white developer (that is, a developer which does not form colored dyes with the coupler compounds) followed by a treatment to fog silver halide (usually chemical fogging or light fogging), followed by treatment with a color developer. Preferred color developing agents are p-phenylenediamines. Especially preferred are:
4-amino N,N-diethylaniline hydrochloride,
4-amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N-(b-(methanesulfonamido) ethylaniline sesquisulfate hydrate,
4-amino-3-methyl-N-ethyl-N-(b-hydroxyethyl)aniline sulfate,
4-amino-3-b-(methanesulfonamido)ethyl-N,N-diethylaniline hydrochloride and
4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidine di-p-toluene sulfonic acid.
Development is followed by bleach-fixing, to remove silver or silver halide, washing and drying.
Synthesis of Dye 2-1
Triethylamine (2.5 g, 0.025 mol) was added in one portion to a stirring slurry of 6-methoxy-2-phenyl-1,3,3-tricyanohexatriene (5 g, 0.02 mol) and 5-phenyl-2-methyl-3-sulfopropylbenzoxozole (6.6 g, 0.02 mol) in 40 mL absolute ethanol at 25 C. The reaction mixture was heated to reflux and held for 30 minutes, then allowed to cool to 25 C. with stirring. The precipitated product was collected by filtration and rinsed with ethanol. The crude dye was slurried in ethanol at reflux, then cooled to 25 C., then collected by filtration to afford 8.6 g (65% yield) of the pure dye 2-1. All analytical data was consistent with the assigned structure.